Create a method that accepts a Graphics object and a Point (for a base point) that draws your cars from within the paint method

Create a Car class that draws itself say in a public draw(Graphics2D g2) method and have your applet hold an ArrayList of these objects, then in paint iterate through the list telling each Car to draw and passing in the current Graphics object

If you create a class to represent a Car object and be responsible for knowing its own position and drawing itself or method to draw a car based on a single position (probably a Point), then you'd be all set.